Real‐world glycaemic outcomes in patients with type 1 diabetes using glucose sensors—Experience from a single centre in Dublin

Abstract Aims To evaluate changes in glycated haemoglobin (HbA1c) and sensor‐based glycaemic metrics after glucose sensor commencement in adults with T1D. Methods We performed a retrospective observational single‐centre study on HbA1c, and sensor‐based glycaemic data following the initiation of continuous glucose monitoring (CGM) in adults with T1D (n = 209). Results We observed an overall improvement in HbA1c from 66 (59–78) mmol/mol [8.2 (7.5–9.3)%] pre‐sensor to 60 (53–71) mmol/mol [7.6 (7.0–8.6)%] on‐sensor (p < .001). The pre‐sensor HbA1c improved from 66 (57–74) mmol/mol [8.2 (7.4–8.9)%] to 62 (54–71) mmol/mol [7.8 (7.1–8.7)%] within the first year of usage to 60 (53–69) mmol/mol [7.6 (7.0–8.4)%] in the following year (n = 121, p < .001). RT‐CGM‐user had a significant improvement in HbA1c (Dexcom G6; p < .001, r = 0.33 and Guardian 3; p < .001, r = 0.59) while a non‐significant reduction was seen in FGM‐user (Libre 1; p = .279). Both MDI (p < .001, r = 0.33) and CSII group (p < .001, r = 0.41) also demonstrated significant HbA1c improvement. Patients with pre‐sensor HbA1c of ≥64 mmol/mol [8.0%] (n = 125), had attenuation of pre‐sensor HbA1c from 75 (68–83) mmol/mol [9.0 (8.4–9.7)%] to 67 (59–75) mmol/mol [8.2 (7.6–9.0)%] (p < .001, r = 0.44). Altogether, 25.8% of patients achieved the recommended HbA1c goal of ≤53 mmol/mol and 16.7% attained the recommended ≥70% time in range (3.9–10.0 mmol/L). Conclusions Our study demonstrated that minimally invasive glucose sensor technology in adults with T1D is associated with improvement in glycaemic outcomes. However, despite significant improvements in HbA1c, achieving the recommended goals for all glycaemic metrics remained challenging.

Input on the glucose sensor type, percentage of time CGM data was captured by sensor, average glucose, glucose management indicator (GMI), coefficient of variation (CV), percentage time in very high range (>13.9 mmol/L), percentage time in high range (10.0-13.9mmol/L), percentage time in range (3.9-10.0mmol/L), percentage time in low range (3.0-3.9 mmol/L) and percentage time in very low range (<3.0 mmol/L) were obtained.Changes in HbA 1 c values before and during sensor use were analysed, along with sensor based glycaemic metrics in accordance with international consensus on GCM reporting guidelines. 14atistical analysis was performed using IBM SPSS Statistics for Macintosh, Version 27 (IBM Corp., Armonk, N.Y., USA).
Nonparametric tests were used for data that was not normally distributed.Wilcoxon signed-rank test was used to compare the most recent HbA 1 c values to the pre-sensor values in all patients, including subgroup analyses based on sensor type and baseline treatment modalities.Similar test was used to compare the changes in HbA 1 c within group of patients who had either a pre-sensor HbA 1 c < 64 mmol/mol [8.0%] or ≥ 64 mmol/mol [8.0%].To indicate the effect size, calculated r was performed with any value of above 0.1, 0.3 and 0.5 indicating small, medium and large effect, respectively.Friedman test was used to compare the changes in HbA 1 c presensor within the first and the second year on-sensor.HbA 1 c within the first and second year on-sensor was defined as the average HbA 1 c within that year.Data are presented as median (interquartile range) or mean ± standard deviation.

| Baseline results
A summary of baseline characteristics of the patients (n = 209) for which the data was collected is presented in    4 and Figure 1).

| HbA 1 c changes based on sensor type
In the Libre (FGM) group (n = 13), there was a nonsignificant reduction in the most recent HbA  5).

| HbA 1 c changes based on baseline diabetes treatment (MDI or CSII)
In  8).   Our study observed a significant improvement in HbA 1 c in the RT-CGM groups (Dexcom G6 and Guardian

TA B L E 2
3) with medium to large effect size.However, such a significant improvement was not observed in the FGM group (Libre).This may be due to a smaller sample size (n = 13).
In a recent meta-analysis, the HbA The tendency of individuals with T1D to maintain a high glucose levels in order to avoid hypoglycaemia, is more commonly observed in individuals with higher HbA 1 c. 17 The use of a glucose sensor has been shown to reduce fear of hypoglycaemia, 18 thus potentially contributing to the greater glycaemic benefits seen in participants with the higher baseline HbA 1 c compared to participants with lower HbA 1 c.
We observed a significant improvement in HbA1c in the MDI and CSII groups, with both exhibiting medium effect size.These findings suggest that the use of glucose sensor provides benefit to both groups.The minor difference in the effect size observed in the CSII group may be attributed to patients familiarity with diabetes technology, the ability to administer a more precise insulin adjustment and utilising sensor-augmented pump therapy with predictive low glucose suspend capabilities including other advanced hybrid closed loop features. 19,20spite observing significant improvements in HbA  the most likely to achieve >70% time in range. 22In recent years, we have seen a widespread use of advanced hybrid closed loop (ACHL) technology that demonstrates real-world success in safely achieving these glycaemic targets, [23][24][25][26] and is a potential tool to further improve the HbA 1 c levels.This trend suggests that the use of insulin pumps and closed loop technologies with glucose sensors may be required, for the more precise glycaemic control required to achieve recommended clinical targets.
The strengths of this study included the real-world nature of the results, the sample size, use of average HbA 1 c values to assess changes during the first and the second year of sensor use, and a high level of sensor data availability.There were several limitations to our study.This was a retrospective observational study evaluating the impact of introducing a glucose sensor, which was limited to Dexcom, Guardian 3 and Libre 1, in unselected patients with T1D attending a diabetes service in a public hospital.Furthermore, patients' options were impacted by the CGM funding at the time in which Libre 1 was approved to patients under 21 years old while Dexcom and Guardian 3 were approved for all ages.Consequently, the cohort of patients that we identified may have affected the data.
Additionally, there are several factors that may contribute to HbA 1 c changes such as diabetes severity index, the presence of diabetes related complications, duration of diabetes, age at diagnosis, rate of DAFNE completion, patients receiving other adjunctive noninsulin therapies, outpatient review frequency and nonattendance rate. 27,28ese factors may need to be controlled in future studies.A small number of patients were using sensor-augmented pump therapy with predictive low glucose suspend capabilities (Medtronic 640G) (n = 12) and advanced hybrid closed loop system (Medtronic 780G) (n = 12).The frequency of attendance for laboratory HbA 1 c measurements may also have been reduced due to the COVID-19 pandemic.Both factors may contribute to the changes in HbA 1 c seen in this study.

| CON CLUS ION
We observed a clinically significant and sustained improvements in

FU N D I N G I N FO R M ATI O N
The author(s) reported there is no funding associated with the work featured in this article.

CO N FLI C T O F I NTER E S T S TATEM ENT
consent for their data to be remotely linked and shared with the diabetes clinic.Data on gender, age, duration of diabetes, types of insulin therapy, HbA 1 c, duration of CGM use and the completion of the Dose Adjustment for Normal Eating (DAFNE) structured diabetes education course were collected.The manufacturers' proprietary webbased glucose monitoring platforms, including Libreview (Abbott Diabetes Care; Oxon, UK), Dexcom Clarity (Dexcom Inc, San Diego, CA, USA) and Carelink (Medtronic Inc, MN, USA) were reviewed.
1 c levels over time with the introduction of glucose sensor technology, achieving the recommended goals for all glycaemic metrics, as defined by the ADA standards of care (2021), 21 remained challenging.In our cohort, 25.8% of patients achieved the recommended HbA 1 c goal of ≤53 mmol/mol [7.0%], while 16.7% achieved the recommended TIR of ≥70% and 91.9% achieved the recommended goal of <4% for time below range.In a multinational cohort study including 5219 children, adolescents, and young adults with T1D, the proportion of individuals achieving the recommended time in range target was found to be associated with treatment modality.Users of RT-CGM concurrently with an insulin pump were TA B L E 6 Patients with pre-sensor HbA 1 c < 64 mmol/mol [8.0%] compared to most recent HbA 1 c.
Summary of sensor-based metric results.

type n Pre CGM HbA 1 c n Most recent HbA 1 c p Value Calculated r
HbA 1 c (mmol/mol) and [%] are expressed in median (IQR).Within-person changes assessed by the Wilcoxon Signed Ranks Test.HbA 1 c change within 2 years of starting a glucose sensor (n = 121).HbA 1 c (mmol/mol) and [%] are expressed in median (IQR).HbA 1 c change assessed by Friedman Test.Pre-sensor HbA 1 c compared to the most recent HbA 1 c by sensor type.
Note:TA B L E 4Note: Note: HbA 1 c (mmol/mol) and [%] are expressed in median (IQR).Within-person changes assessed by the Wilcoxon Signed Ranks Test.
Patients with pre-sensor HbA 1 c ≥ 64 mmol/mol compared to most recent HbA 1 c.Pre-sensor HbA 1 c compared to the most recent HbA 1 c by diabetes treatment type.HbA 1 c (mmol/mol) and [%] are expressed in median (IQR).Within-person changes assessed by the Wilcoxon Signed Ranks Test.
TA B L E 8Abbreviations: CGM, continuous glucose monitor; CSII, continuous subcutaneous insulin infusion; HbA 1 c, glycated haemoglobin; MDI, multiple daily injection; n, number.Note: REL, RAW, SYG, AR, MOS, HJK, KN, DOS, RC and WAWM declare no conflict of interest.CB declares receiving honoraria for educational events and conference attendance from Astra Zeneca, Behaviour Change Training Ltd., Diabetes Ireland, EASO, International Medical Press, Eli Lily, Medscape, MSD, Novo Nordisk and Sanofi Aventis and is a former member of a Dexcom Advisory Board.She is a member of an Obesity National Clinical Programme Clinical Advisory Group, and MECC working group in Ireland.